1. Field of the Invention
The present invention relates to a scanner motor coupled with a polygon mirror employed for a laser beam printer, and more particularly to a structural improvement of coupling a housing fixedly installed to an upper end of a motor shaft with a polygon mirror coupled to the housing.
2. Description of the Prior Art
Generally, a laser beam printer employs an optical scanning device which is provided with a rotating polygon mirror, and it is a scanner motor to rotate the polygon mirror.
The scanner motor is for widely reflecting the light emitted from a laser diode toward a photosensitive drum. Since the above-stated polygon mirror demands high rotating precision, it is necessary to maintain the highly stable rotating state thereof. Furthermore, the polygon mirror itself should not to be pressurized to thus require a particular coupling structure.
The scanner motor is typically formed by, as shown in FIG. 1, a plate 1 fixed with a stator assembly 2 wound with coils, a cylinder 3 provided by being inserted into a hole formed in the center of plate 1. A motor shaft 5 is erectly formed by interposing a bearing 4 at the center of cylinder 3, and a housing 6 is coupled to the upper end of motor shaft S. Additionally, a rotor case 7 is separately joined to the lower end of housing 6, and a polygon mirror 8 is inserted into the upper end of housing 6 to be coupled thereto.
In the conventional scanner motor constructed as above, once an electric power is applied to stator assembly 2, a magnetic force is incited by the interaction with a magnetic body installed into the inside of rotor case 7 which is in turn rotated at high speed by centering about motor shaft 5. During this operation, polygon mirror 8 becomes rotated to deflect beams which scan toward polygon mirror 8 by a constant angle of view.
In order to prevent the deviation of polygon mirror 8, the foregoing conventional motor employs an elastic clamp 9 as shown in FIG. 1. That is, elastic clamp 9 is for pressing the upper plane of polygon mirror 8 with its radially-split edge end 9a in such a manner that the center portion of elastic clamp 9 is inserted into the upper end of motor shaft 5 to confine polygon mirror 8 by means of a screw 91 coupled into the upper end plane of motor shaft 5.
The reason for using elastic clamp 9 is that housing 6 and polygon mirror 8 are loosely fitted to each other so as not to transfer the pressing force upon polygon mirror 8. Accordingly, elastic clamp 9 is utilized to press the upper portion of polygon mirror 8 to inhibit the deviation of the loosely-fitted polygon mirror 8 during the rotating motion.
However, in the above-described conventional coupling structure, elastic clamp 9 is necessarily required as well as screw 91 coupled into motor shaft 5 after inserting elastic clamp 9 into motor shaft 5. Furthermore, there is a problem of separately processing a female screw into motor shaft 5 for attaining the screw coupling. Therefore, the aforementioned conventional structure deleteriously involves many problems such as the increased number of parts, lengthened manufacturing process and man-hour, fastidious designing with respect to the coupling of the elastic clamp and raised cost.
In order to solve the above-stated problems, Japanese Patent Laid-Open Publication No. Hei 6-55113 has suggested a polygon mirror fixing structure. Here, a recess is formed into a reference plane of a rotating body which is fixed with the polygon mirror to be integrally rotated, and an adhesive is coated over the recess to fixedly adhering the polygon mirror to the rotating body. But, it has a drawback of degrading practicability because of difficulty in setting the hardening time and hardening temperature of the adhesive and restricted range of selecting the kind of adhesive.